Locking Windows Proxy Settings Does Not Enforce Proxy Use

If the requirement is “users should not edit this managed proxy setting,” use the supported management policy for that setting. If it is “all application traffic must use this exit,” you have another requirement as well.

Microsoft documents a proxy-change restriction through the Internet Explorer policy CSP's DisableProxyChange setting. Check its supported scope, operating systems, and management format. An old recipe that hides an entire Connections page is not a precise description of every current proxy-policy interface.

The policy controls configuration access. It does not transform arbitrary network operations into HTTP proxy requests. An application can use a separate documented networking configuration or a protocol outside that web-proxy path.

Define those two outcomes separately: who can change the managed configuration, and which outbound connections the network permits. Authentication to the proxy is another control again.

For a managed deployment, keep the intended applications and required traffic in scope when assessing the result. A greyed-out settings panel proves something about that panel. It is not a measurement showing that every process now uses the same exit IP.